Methods of analyzing a sample include methods in which the reaction liquid resulting from the reaction of a sample and a reagent is analyzed by optical means. Such analysis is accomplished for example by mounting an analyzing instrument which provides a reaction field on an analyzing apparatus equipped with an optical system capable of emitting and receiving light (see for example JP-A 8-114539). In this case, it is desirable to adjust the temperature of the analyzing instrument (particularly the reaction liquid), and to react the sample and reaction liquid at roughly the same temperature for each measurement so as to minimize analysis error and increase the reliability of the analysis results. In systems using enzyme reactions in particular, because the reaction speed is highly temperature-dependent the temperature of the system is preferably adjusted to within ±0.1° C. of the target temperature.
Methods of adjusting the temperature of a reaction liquid include for example the method illustrated in FIG. 9A in which analyzing instrument 9 is held on heat block 91, which had a greater heat capacity than reaction liquid 90, and the temperature of reaction liquid 90 is adjusted by controlling the temperature of this heat block 91 (see for example JP-A 9-189703 and JP-A 10-253536). In this method, the temperature of reaction liquid 90 is monitored by means of temperature sensor 92 embedded in heat block 91 for example, and when the temperature of reaction liquid 90 falls below a specified value, heat block 91 is heated to raise its temperature, thus raising the temperature of reaction liquid 90 via heat block 91. Moreover, as shown in FIG. 9B there is another method in which analyzing instrument 9 is held on heat generator 93, which has high temperature continuity, and the temperature of reaction liquid 90 is directly adjusted by means of this heat generator 93 (see for example JP-A 9-304269). In this method as well, heat generator 93 is driven in accordance with the monitoring results from temperature sensor 92 to control the temperature of reaction liquid 90.
These temperature control methods have the drawback of high energy consumption because it is necessary to heat block 91 or drive heat generator 93 when raising the temperature of reaction liquid 90. Moreover, with heating media such as heat block 91 and heat generator 93, it is difficult to exactly heat only that region where reaction liquid 90 is held when the amount of reaction liquid 90 is small as in a microdevice. Consequently, heating media 91 and 93 need to be relatively large in comparison with the region that needs to be heated (the region directly below reaction liquid 90 in the figure) in order to raise the temperature of reaction liquid 90 with good responsiveness. As a result, when controlling the temperature of a reaction liquid in microdevice energy efficiency is poor because the amount of heat used for raising the temperature of reaction liquid 90 is small in comparison with the amount of heat transmitted by heating media 91 and 93.
Thus, conventional temperature control methods have had the drawback of high energy consumption. Consequently, it has been difficult to apply conventional temperature control methods to analyzing apparatuses driven by internal power sources such as small batteries (for example, batteries widely used for household use), and even if the aforementioned methods were applied to a small analyzing apparatus it would not be practical because the actual working time of the analyzing apparatus would be extremely short. And while the shortness of the actual working time can be improved by increasing the capacity of the internal power source, this impedes miniaturization of the analyzing apparatus and detracts from wide use. Power can also be supplied from an external source, but in that case an adapter is necessary to connect the analyzing apparatus to the external power source, making it less portable and also creating problems for use in other locations.